The present disclosure relates to systems for transferring heat for use onboard a vehicle, and in particular to onboard vehicle heat sources. More particularly, the present disclosure relates to heat exchangers for motor vehicle exhaust.
Vehicles have systems for managing heat. Some of these systems are used to recover heat from vehicle exhaust gas. The recovered heat is then used to heat desired regions of the vehicles.
A heat transfer system in accordance with the present disclosure is to be carried onboard a motor vehicle to extract heat from a heat source and to transfer the extracted heat to a heat carrier. The heat source is, for example, exhaust gas discharged from the engine of the vehicle and the heat carrier is, for example, liquid engine coolant fluid which carries the heat extracted from exhaust gas to a vehicle heating and defrosting system, for example, to warm a passenger cabin or defrost a windshield.
To maximize heat transferred from exhaust gas to engine coolant fluid, the heat transfer system induces the engine to work harder to provide a desired output (measured, for example, in rpm""s or revolutions per minute). It induces the engine to work harder by routing exhaust gas along a tortuous or serpentine path. This generates a resistance or back pressure felt by the engine as an additional load. When the engine works harder because of this additional load, exhaust gas discharged from the engine is hotter. Hotter exhaust gas means that more heat is transferred from exhaust gas to engine coolant fluid causing the engine coolant fluid to be hotter also. When engine coolant fluid is hotter, the passenger cabin can be heated more quickly and the windshield can be defrosted more quickly. This is particularly useful in cold weather.
The heat transfer system includes exhaust conductor means for conducting exhaust gas discharged from an engine along a serpentine path to generate back pressure for transmission to the engine discharging exhaust gas to an annular outer exhaust gas passageway so that heat of exhaust gas discharged into the annular outer exhaust gas passageway is maximized. The serpentine path passes in series through the annular outer exhaust gas passageway in a first direction, an annular intermediate exhaust gas passageway in a second direction opposite to the first direction, and an inner exhaust gas passageway in the first direction. The heat transfer system further includes fluid conductor means for conducting a fluid through the outer exhaust gas passageway to heat the fluid using heat from the exhaust gas passing through the annular outer exhaust gas passageway and providing the heated fluid for use in a vehicle heating and defrosting system onboard the vehicle.
The exhaust conductor means includes three tubes which can be referred to as a housing, an intermediate tube, and an inner tube. The housing surrounds the intermediate tube and the inner tube, and the intermediate tube surrounds the inner tube. The housing and the intermediate tube cooperate to provide the outer exhaust gas passageway therebetween. The intermediate tube and the inner tube cooperate to provide the intermediate exhaust gas passageway therebetween. The inner tube is formed to include the inner exhaust gas passageway.
The fluid conductor means is a coil extending through the outer exhaust gas passageway. The coil surrounds the intermediate and inner tubes.
Additional features of the present disclosure will become apparent to those skilled in the art upon consideration of the following detailed description of illustrative embodiments exemplifying the best mode of carrying out the invention as presently perceived.